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Makemake laid bare in rare occultation

Jenny Winder, News Writer
Nov 27, 2012, 8:00 UTC

Sen—Makemake is one of five dwarf planets in our Solar System, including former planet Pluto, Ceres, Haumea and Eris, the most massive and the most distant. All except Makemake have been studied.

Now, using a barrage of ground based telescopes, astronomers have finally managed to observe the dwarf planet as it blocked the light of distant star, Nomad 1181-0235723. Such stellar occultations are rare in the case of Makemake because it orbits in an area of sky that has relatively few stars. This occultation took place on April 23, 2011 and lasted for no more than a minute.

Makemake was first discovered during Easter in March 2005. In July 2008 it was officially named Makemake after the creator of humanity and god of fertility of the native people of Easter Island. It travels around the Sun in a distant path that lies between that of Pluto and Eris.

The multiple observations used telescopes of the European Southern Observatory (ESO) at La Silla and Paranal in Chile, the Very Large Telescope (VLT), New Technology Telescope (NTT), and TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope).

It had been thought that Makemake would have an atmosphere similar to that of Pluto but leader of the Team of Astronomers, Jose Luis Ortiz of the Instituto de Astrofisica de Andalucia, CSIC, Spain explained "As Makemake passed in front of the star and blocked it out, the star disappeared and reappeared very abruptly, rather than fading and brightening gradually. This means that the little dwarf planet has no significant atmosphere."

"It was thought that Makemake had a good chance of having developed an atmosphere - that it has no sign of one at all shows just how much we have yet to learn about these mysterious bodies. Finding out about Makemake's properties for the first time is a big step forward in our study of the select club of icy dwarf planets." Although Makemake shows no global atmosphere, it may have an atmosphere that only covers part of the surface.

The observations taken during the occultation also gave more accurate details of the dwarf planet's size, showing it to be an oblate spheroid measuring 1,430 km by 1,500 km, making it about two-thirds the size of Pluto. It has a density of 1.7 grams per cubic centimetre like Pluto's, but less than a third that of Earth. Astronomers also measured how much of the Sun’s light Makemake’s surface reflects, the albedo, to be 0.77 which is similar to dirty snow and greater than Pluto's, but smaller than that of Eris.

"Pluto, Eris and Makemake are among the larger examples of the numerous icy bodies orbiting far away from our Sun," says Jose Luis Ortiz. "Our new observations have greatly improved our knowledge of one of the biggest, Makemake - we will be able to use this information as we explore the intriguing objects in this region of space further."